// 宽高
.wh (@width, @height) {
    width: @width;
    height: @height;
}
// 背景图片地址和大小
.bis (@url) {
    background-image: url(@url);
    background-repeat: no-repeat;
    background-size: 100% 100%;
}

// flex 布局
.flex (@flex-direction, @align-items, @justify-content) {
    display: flex;
    flex-direction: @flex-direction;
    align-items: @align-items;
    justify-content: @justify-content;
}

